Gears of War's cover and concealment and BioShock's Plasmid abilities are concepts around which developers designed whole games. Concepts, not gimmicks, because gimmick connotes cheapness, because gimmick implies a ruse or last resort, as in the game isn't good enough on its own and needs something extra to sell it. Neither of the features named above fits that bill. You can't grouse about Plasmids apart from BioShock's other qualities since both the first-person shooter's enemies and frozen or flooded environments thoroughly tie into the player's fire and electric powers. Battlefield: Bad Company's destructible buildings, trees, terrain, and bridges ought to amount to something of similar magnitude.